Can electric generator produce any combo of MVARs and MWs

[chris00nj]

Can an electric generator produce any combination of MVARs and MWs such that the MVA output doesn't exceed the rating?

If I have an generator that has a rated output of 115 MVA (GE 7A6), can I produce any combination of MWs and MVARs to my preference such that the power triangle equals 115 MVA?

For example, could I go from:
100 MW & 56 MVAR = 115 MVA
to
86 MW & 76 MVAR = 115 MVA

 

[dpc]

Sort of, but not quite. There will be Generator Capability Curve that defines limits for operation from lagging to leading power factor. You need to stay within this curve.



David Castor

http://www.cvoes.com

 

[cranky108]

There are three sets of curves that govern the maximum allowed output of a generator. The capability curve, which reflects the heating limits of the stator. The var limit curve, which relfects the thermal limits of the rotor. And the stability curve, which reflects the lower limit of stability for the field.

 

[ScottyUK]

The combined locus of the curves is generally referred to as the capability diagram. There actually quite a few separate curves - a lot more than three - but the three listed above give the basic shape. One very important one is the stator end heating curve. Why is it important? Well most machines don't have temperature sensors in the end region so that region can be in big trouble without any untoward readings from the stator core RTDs.

A while ago I uploaded an old CEGB document which is a fantastic reference for anyone wanting to understand capability diagrams.


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If we learn from our mistakes I'm getting a great education!

 

[cranky108]

Scotty, There is some newer technology in fiberoptic tempeture monitoring. Have you seen any applications in newer generation?

I have heard of it applied to power transformers, at the predicted hot spot. But I also haven't seen it applied on the new transformers I've seen.
And just maybe it did not work out.

 

[ScottyUK]

When I was with my previous employer (consulting engineers to the power industry) we were speccing fibre monitoring to be incorporated in the GSU transformer windings. Much of that work was for the middle east, and those guys have the money to pay for all the toys so their specs usually require a lot of auxiliary equipment which we don't seem to see in Europe so much. I'm aware of fibre being used for temperature monitoring in EHV cables too but I'm not a cables guy and hopefully someone from the transmission industry can comment a bit more about that.

I've not heard of fibre being deployed for monitoring generator windings although it seems an ideal application given the total immunity to E-M interference.


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If we learn from our mistakes I'm getting a great education!